2001 Ford F-150 Tapping Sound at all RPM

RBDOG70

MEMBER
2001 FORD F-150
V8
2WD
AUTOMATIC
148,000 MILES

My Triton 4.6L V8 engine recently developed a tapping sound that increases in frequency with increased RPM (about 3-4 times per second at idle and in gear, i.E. Such as stopped at an intersection).
I thought the tapping sound might be a tappet or lifter issue, but upon inspection under the hood, the sound seems to be originating more from the front of the the engine rather than from the side - cylinder heads. The tapping sound is fairly noticable from inside the cab (windows up). The oil was changed (5W-20 - Synthetic) 14 days ago and about 350 driving miles since. Actually noticed the tapping sound after the oil change, but it may have been occurring before that. No other issues with starting, performance or recent fuel mileage.
What what would you suggest be inspected, tested or replaced?

As an aside, my research into diagnosing this issue turned up significant reports of "spark plug blowout" on the Triton engine as far back as 1997 (a condition that seems to be routinely disregarded by Ford corporate?), With one account of a "tapping" sound just prior to the "blowout". I've seen no simiilar reports of spark plug blowout in this forum, but wonder if I may be overlooking a "loose" or loosening plug problem even though my triangulation of the tapping sound pointed me to the front of the engine?

1 Reply

MERLIN2021

MECHANIC
17,250 POSTS

Sound is funny that way, it might actually be the plug problem, and sound tranference is leading you away from that. With 148,000 miles, a cam follower may be slipping or the plug, or even a frayed serpentine belt, have you checked the belt? If it's old, remove the belt, inspect it fot cracks or frayed sections, and while the belt is off, spin all the pulleys, alt, a/c, idler, and tensioner, if you feel any roughness or grinding, you have a bad bearing in that pulley, replace it. You can also try unplugging the Coil on plug at each plug, one at a time and see if the sound changes, BE VERY careful, if it is a failing thread on a plug, they can blow out with enough force to kill you if your face is above it!